As a method for producing an optically active (4R)-1,3-thiazolidine-4-carboxylic acid, a method that comprises cyclizing L-cysteine and L-penicillamine used as starting materials with formaldehyde is described in Japanese Patent Laid-open Publication (Kokai) No. 6-247948. However, this method is not considered as an industrially advantageous method since it uses expensive reagents.
There has not been reported any method for producing an optically active (4R)-1,3-thiazolidine-4-carboxylic acid by hydrolyzing 1,3-thiazolidine-4-carboxylic acid amide utilizing a microorganism or enzyme of microorganism. Moreover, there has not been reported any method for racemizing an optically active (4S)-1,3-thiazolidine-4-carboxylic acid amide.